Hemoglobin A1c and the Progression of Coronary Artery Calcification Among Adults Without Diabetes

OBJECTIVE Higher levels of hemoglobin A 1c (HbA 1c ) are associated with increased cardiovascular disease risk among individuals without diabetes and may also be positively associated with coronary artery calcification (CAC). This study investigated the association of HbA 1c with CAC progression in the Coronary Artery Risk Development in Young Adults study. RESEARCH DESIGN AND METHODS We included 2,076 participants with HbA 1c and noncontrast computed tomography (CT) assessed at baseline (2005–2006), and CT repeated 5 years later (2010–2011). CAC progression was defined as 1 ) incident CAC (increase >0 Agatston units among those with no CAC at baseline), 2 ) any CAC progression (increase >10 Agatston units between examinations), and 3 ) advanced CAC progression (increase >100 Agatston units between examinations). RESULTS During the 5-year follow-up period, 12.9% of participants without baseline CAC developed incident CAC; among all participants, 18.2% had any CAC progression and 5.4% had advanced CAC progression. Higher HbA 1c was associated with incident CAC (risk ratio [RR] = 1.45; 95% CI 1.02, 2.06), any CAC progression (RR = 1.51; 95% CI 1.16, 1.96), and advanced CAC progression (RR = 2.42; 95% CI 1.47, 3.99) after adjustment for sociodemographic factors. Additional adjustment for cardiovascular risk factors attenuated the associations of HbA 1c with incident CAC (RR = 1.05; 95% CI 0.74, 1.49) and any CAC progression (RR = 1.13; 95% CI 0.87, 1.47). In contrast, the association of HbA 1c with advanced CAC progression persisted in multivariable adjusted models (RR = 1.78; 95% CI 1.08, 2.95). CONCLUSIONS Higher HbA 1c was independently associated with advanced CAC progression among individuals without diabetes, while the associations with incident CAC and any CAC progression were accounted for by other established cardiovascular risk factors.